gps303/lookaside.py

   1 """ Estimate coordinates from WIFI_POSITIONING and send back """
   2
   3 from datetime import datetime, timezone
   4 from logging import getLogger
   5 from os import umask
   6 from struct import pack
   7 import zmq
   8
   9 from . import common
  10 from .gps303proto import parse_message, WIFI_POSITIONING
  11 from .opencellid import qry_cell
  12 from .zmsg import Bcast, Resp, topic
  13
  14 log = getLogger("gps303/lookaside")
  15
  16
  17 def runserver(conf):
  18     if conf.get("lookaside", "backend") != "opencellid":
  19         raise NotImplementedError(
  20             "Lookaside only implements opencellid backend"
  21         )
  22     zctx = zmq.Context()
  23     zsub = zctx.socket(zmq.SUB)
  24     zsub.connect(conf.get("collector", "publishurl"))
  25     zsub.setsockopt(zmq.SUBSCRIBE, topic(WIFI_POSITIONING.PROTO))
  26     zpush = zctx.socket(zmq.PUSH)
  27     zpush.connect(conf.get("collector", "listenurl"))
  28
  29     try:
  30         while True:
  31             zmsg = Bcast(zsub.recv())
  32             msg = parse_message(zmsg.packet)
  33             log.debug(
  34                 "IMEI %s from %s at %s: %s",
  35                 zmsg.imei,
  36                 zmsg.peeraddr,
  37                 datetime.fromtimestamp(zmsg.when).astimezone(tz=timezone.utc),
  38                 msg,
  39             )
  40             lat, lon = qry_cell(
  41                 conf["opencellid"]["dbfn"], msg.mcc, msg.gsm_cells
  42             )
  43             resp = Resp(
  44                 imei=zmsg.imei,
  45                 when=zmsg.when,  # not the current time, but the original!
  46                 packet=msg.Out(latitude=lat, longitude=lon).packed,
  47             )
  48             log.debug("Response for lat=%s, lon=%s: %s", lat, lon, resp)
  49             zpush.send(resp.packed)
  50
  51     except KeyboardInterrupt:
  52         pass
  53
  54
  55 if __name__.endswith("__main__"):
  56     runserver(common.init(log))